Preparation and optical properties of GaN nanocrystalline powders

Abstract

GaN nanocrystalline powders were synthesised by decomposition of gallium nitrate, followed by nitrogenising with ammonia under different temperature. X-ray diffraction (XRD) and the transmission electron microscopy (TEM) indicated that the crystallinity of the powder is improved and the average size of the GaN nanocrystallites increases from 4·8 to 23·9 nm as the temperature increases from 850 to 1050°C. The Raman spectra displayed four broadened peaks corresponding to A1 (LO), A1 (TO), E1 (TO) and E2 (high) modes of würtzite GaN respectively. Two additional modes at 252 and 421 cm–1 attributed to boundary phonons activated by the finite size effects and octahedral Ga–N6 bonds were observed respectively. A strong blue photoluminescence (∼353 nm) was detected for room temperature measurement, indicating that the GaN nanocrystalline powders have few defects and high quality.